Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: 2ª carreira/salário de professor substituto ($20.000) envolve o que 6ª carreira/salário?
 ###Tabelas: CREATE TABLE winners_of_the_allaire_dupont_distaff_stakes_since_1992 (winners_of_the_allaire_dupont_distaff_stakes_since_1992_id AUTO_INCREMENT PRIMARY KEY, Year INT, Winner VARCHAR, Jockey VARCHAR, Trainer VARCHAR, Owner VARCHAR, Distance VARCHAR, Time VARCHAR, Purse VARCHAR) CREATE TABLE mixed_team_event (mixed_team_event_id AUTO_INCREMENT PRIMARY KEY, Team VARCHAR, Female épée VARCHAR, Male épée VARCHAR, Female foil VARCHAR, Male foil VARCHAR, Female saber VARCHAR, Male saber VARCHAR, Average fencers rank VARCHAR, Initial Team rank INT) CREATE TABLE careers (careers_id AUTO_INCREMENT PRIMARY KEY, Career Card VARCHAR, Starting career/salary VARCHAR, 2nd career/salary VARCHAR, 3rd career/salary VARCHAR, 4th career/salary VARCHAR, 5th career/salary VARCHAR, 6th career/salary VARCHAR) CREATE TABLE atp_doubles_finals:_13_6–7 (atp_doubles_finals:_13_6–7_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Date VARCHAR, Tournament VARCHAR, Surface VARCHAR, Partnering VARCHAR, Opponents in the final VARCHAR, Score VARCHAR) CREATE TABLE parliamentary_elections (parliamentary_elections_id AUTO_INCREMENT PRIMARY KEY, Election date INT, Party leader VARCHAR, Number of votes received INT, Percentage of votes VARCHAR, Number of deputies INT)  
SELECT 6th career/salary FROM careers WHERE 2nd career/salary = substitute teacher ($20,000)